Wrenches and other hand tools often can not exert enough force to grip an object securely. In the case of wrenches, rusted, frozen and undersized nuts are often difficult to remove and become further deformed by the action of the wrench jaws. Wire cutters and other hand tools that apply an increasing force on an object between jaws of a hand tool often lack sufficient mechanical advantage to function with wire of more than a small gage.
Pliers, socket wrenches, open end wrenches, vise grips type devices and pipe wrenches are well known.
Wrenches which function as an approximation of the nut head, such as open end wrenches and socket wrenches, must by necessity be slightly oversized so that they can accommodate a rusted nut and so that they can be applied and removed easily. This mismatch between the nut head and the wrench face will tend to reduce mechanical efficiency and limit the gripping force exerted upon the faces of the nut. Likewise traditional wire cutters have a limited leverage and force which can be exerted on the wire or other material to be cut when inserted between jaws of the tool.
Vise grip tools enable an adjustable degree of leverage to increase pressure on the object grasped. Problems with the vise grip include high pressure on the handles in order to get a tight grip, a tendency to distort or destroy the surface of the object gripped, high pressure required to release the grip, and lack of any feedback or “mechanic's feel” when using the vise grip.
Traditional pliers are usually made to fit a large range of sizes of nut or object to be gripped. Conventional pliers are severely limited in the amount of mechanical advantage they provide and often strip nut heads because of the mechanical force fed back into the handles when the closed pliers is turned forces the handles open and releases the grip on the nut.